Method for producing aromatic nitrile compound and method for producing carbonate ester

ABSTRACT

The present invention provides a method for producing an aromatic nitrile compound, the method comprising a dehydration reaction wherein a desired compound can be selectively obtained with high yield while suppressing the generation of by-products during the regeneration of an aromatic amide compound into the corresponding aromatic nitrile compound. In addition, the present invention realizes a method for efficiently producing a carbonate ester by applying the abovementioned production method to a method for producing a carbonate ester. The above are achieved by means of a method for producing an aromatic nitrile compound involving a dehydration reaction wherein an aromatic amide compound is dehydrated, the method having a contact step for bringing the aromatic amide compound into contact with a catalyst in a gas phase during the dehydration reaction.

TECHNICAL FIELD

The present invention relates to a method for producing an aromaticnitrile compound such as cyanopyridine and a method for producing acarbonate ester.

BACKGROUND ART

“Carbonate ester” is a general term for a compound obtained bysubstituting one or both of two hydrogen atoms in carbonic acid CO(OH)₂with an alkyl group or an aryl group, and it has a structure ofRO—C(═O)—OR′ (R and R′ represent a saturated hydrocarbon group or anunsaturated hydrocarbon group).

A carbonate ester is used as an additive, for example, a gasolineadditive for improving the octane value and a diesel fuel additive fordecreasing the amount of particles in exhaust gas. A carbonate ester isalso used as, for example, an alkylation agent, a carbonylation agent, asolvent or the like for synthesizing resins or organic compounds such aspolycarbonate, urethane, pharmaceutical drugs, agricultural chemicals orthe like, a material of an electrolytic solution of lithium ion cells, amaterial of lubricant oil, or a material of an oxygen absorber for rustinhibition of boiler pipes. As can be seen, a carbonate ester is a veryuseful compound.

As a conventional method for producing a carbonate ester, a method fordirectly reacting phosgene, which is used as a source of a carbonyl,with an alcohol is mainly employed. Phosgene used in this method ishighly hazardous and highly corrosive, and therefore, needs extremecaution when being handled, for example, transported or stored. It ishighly costly to control and manage, and guarantee the safety of,production facilities of phosgene. Further, in the case of theproduction using this method, raw materials and catalysts containhalogen such as chlorine, and the obtained carbonate ester contains atrace amount of halogen, which cannot be removed by a simplepurification step. When the carbonate ester is used for a gasolineadditive, a light oil additive or an electronic material, such halogenmay undesirably cause corrosion. For this reason, a thoroughpurification step is indispensable to decrease the trace amount ofhalogen present in the carbonate ester to the level of an extremelytrace amount. Moreover, recently, administrative offices provide astrict administration guidance and do not permit new establishment ofproduction facilities using this method because this method utilizesphosgene, which is highly hazardous to the human body. Accordingly, anew method for producing a carbonate ester that does not use phosgene isstrongly desired.

A method for directly synthesizing a carbonate ester from an alcohol andcarbon dioxide using a heterogeneous catalyst is also known. Regardingthis method, studies had been made on using 2-cyanopyridine orbenzonitrile as a wettable powder to significantly improve theproduction amount and the production speed of the carbonate ester, toallow the reaction to advance easily under a pressure close to ordinarypressure, and to increase the reaction speed (see Patent Documents 1 and2). However, there was a problem regarding the method for treating orutilizing benzamide or the like generated as a by-product.

For example, use of benzamide generated by the reaction betweenbenzonitrile and water is limited to some of pharmaceutical andagrochemical intermediates. Thus, use of benzamide is limited to someextent. Therefore, in the production of a carbonate ester usingbenzonitrile as a wettable powder, benzamide by-produced is desired tobe regenerated into benzonitrile and reused. It is now an issue torealize a regeneration reaction with high selectivity (because it isconsidered that if a by-product is generated, it is difficult to reusebenzonitrile as a wettable powder) and a high yield (because if theyield is low, benzamide remains in a large amount, which increases theamount of work, namely, work load, of separating benzamide andbenzonitrile from each other).

In consideration of the above-described problems regarding theregeneration of benzamide or the like into benzonitrile or the like,there is a known method for performing the above-described regenerationnot using a strong reagent while suppressing the generation of aby-product (Patent Document 3).

However, according to this method, generation of nitrile by means ofdehydration of an amide compound requires 400 hours and therefore cannotbe balanced with, namely, cannot be used in combination with, acarbonate ester synthesis reaction, which requires only 24 hours. Thismethod also has a problem that steps of extraction, infiltration and thelike are necessary for solid-liquid separation of a catalyst, resultingin a complicated process having many steps.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: Japanese Laid-Open Patent Publication No.    2010-77113-   Patent Document 2: Japanese Laid-Open Patent Publication No.    2012-162523-   Patent Document 3: WO2015/099053

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In consideration of the above-described problems of prior art, an objectof the present invention is to provide a method which enables adehydration reaction, wherein a desired compound can be selectivelyobtained with high yield while suppressing the generation of by-productsduring the regeneration of an aromatic amide compound such aspyridinecarboamide into cyanopyridine that is a corresponding aromaticnitrile compound. Another object of the present invention is to providea method for producing an aromatic nitrile compound, which can decreasethe number of steps of the dehydration reaction and significantlyimprove the reaction speed to shorten the reaction time.

A still another object of the present invention is to apply theabove-described method for producing an aromatic nitrile compound to acarbonate ester production method to realize a method for efficientlyproducing a carbonate ester.

Means for Solving the Problems

In order to solve the above-described problems, the present inventorsmade researches regarding a method for producing an aromatic nitrilecompound such as cyanopyridine by means of dehydration of an aromaticamide compound. The present inventors examined reaction conditions fordehydration of the aromatic amide compound, and realized a dehydrationreaction process, wherein, by bringing the aromatic amide compound inthe form of gas or mist into contact with a catalyst in a gas phase in ashort time, the reaction speed can be significantly improved to shortenthe reaction time, and in addition, a desired compound can beselectively obtained with high yield while suppressing the generation ofby-products.

According to the above-described present invention, it is possible toimprove the rate of regeneration of the aromatic amide compound into thearomatic nitrile compound by means of the dehydration reaction, and thedehydration reaction and the rate of synthesis of a carbonate ester fromCO₂ and an alcohol using the aromatic nitrile compound can beestablished as a series of efficient commercial processes. The presentinventors also made researches for applying the above-described findingto a carbonate ester production method. As a result, also in a methodfor producing a carbonate ester in which the carbonate ester is directlysynthesized from an alcohol and carbon dioxide, it was confirmed thatbeneficial effects are obtained when an aromatic nitrile compound isefficiently regenerated by a contact step in which an aromatic amidecompound in the form of gas or mist is brought into contact with acatalyst in a gas phase in a short time. The gist of the presentinvention is as described below.

(1) A method for producing an aromatic nitrile compound, the methodcomprising a dehydration reaction, wherein an aromatic amide compound isdehydrated,

-   -   the method having a contact step for bringing the aromatic amide        compound into contact with a catalyst in a gas phase during the        dehydration reaction.        (2) The method for producing an aromatic nitrile compound        according to item (1), wherein the catalyst includes an alkali        metal.        (3) The method for producing an aromatic nitrile compound        according to item (1) or (2), wherein the aromatic amide        compound includes at least a heteroaryl amide compound, and        wherein the aromatic nitrile compound includes at least a        heteroaryl nitrile compound.        (4) The method for producing an aromatic nitrile compound        according to item (3), wherein the heteroaryl amide compound        includes 2-picolinamide, and wherein the heteroaryl nitrile        compound includes 2-cyanopyridine.        (5) The method for producing an aromatic nitrile compound        according to any one of items (1) to (4), wherein in the contact        step, an inert gas and/or a solvent in a vaporized state is        further brought into contact with the catalyst.        (6) The method for producing an aromatic nitrile compound        according to item (5), wherein the inert gas includes at least        nitrogen gas.        (7) The method for producing an aromatic nitrile compound        according to item (5) or (6), wherein the boiling point of the        solvent under ordinary pressure is 20° C. to 300° C.        (8) The method for producing an aromatic nitrile compound        according to any one of items (5) to (7), wherein the solvent is        compatible with the aromatic amide compound.        (9) The method for producing an aromatic nitrile compound        according to any one of items (5) to (8), wherein the solvent        includes a pyridine compound and/or a cyclic ketone.        (10) The method for producing an aromatic nitrile compound        according to any one of items (1) to (9), wherein in the contact        step, the temperature at which the aromatic amide compound is        brought into contact with the catalyst in the gas phase is        170° C. or higher but lower than 300° C.        (11) The method for producing an aromatic nitrile compound        according to any one of items (1) to (10), wherein the time for        bringing the aromatic amide compound into contact with the        catalyst in the gas phase is 0.001 sec or more but less than 10        sec.        (12) A method for producing a carbonate ester, which has:

a first reaction step that includes: a carbonate ester productionreaction in which an alcohol is reacted with carbon dioxide in thepresence of an aromatic nitrile compound to produce the carbonate esterand water, and a hydration reaction in which the aromatic nitrilecompound is hydrated with the produced water to produce an aromaticamide compound; and

a second reaction step in which the aromatic amide compound is separatedfrom the reaction system of the first reaction step and then thearomatic amide compound is regenerated into an aromatic nitrile compoundby means of a dehydration reaction for dehydrating the aromatic amidecompound, the dehydration reaction having a contact step for bringingthe aromatic amide compound into contact with a catalyst in a gas phase,

wherein at least a part of the aromatic nitrile compound regenerated inthe second reaction step is used in the first reaction step.

(13) The method for producing a carbonate ester according to item (12),wherein in the second reaction step, an aromatic nitrile compound isproduced from the aromatic amide compound according to the method forproducing an aromatic nitrile compound according to any one of items (2)to (11) to regenerate the aromatic nitrile compound.(14) The method for producing a carbonate ester according to item (12)or (13), wherein a catalyst including cerium oxide is used in thecarbonate ester production reaction.(15) The method for producing a carbonate ester according to any one ofitems (12) to (14), wherein the alcohol includes an alcohol having 1 to6 carbon atoms.

Advantageous Effect of the Invention

According to the present invention, it is possible to efficiently carryout the production (regeneration) of an aromatic nitrile compound suchas cyanopyridine from an aromatic amide compound such aspyridinecarboamide (picolinamide, nicotinamide, etc.) and benzamide.Specifically, in a dehydration reaction of the aromatic amide compoundfor the above-described regeneration, the generation of by-products canbe suppressed, a desired compound can be selectively obtained with highyield, and a reaction rate can be improved. Therefore, according to thepresent invention, the reaction time of the dehydration reaction forregenerating the aromatic nitrile compound can be significantly reducedwhen compared to conventional methods. Moreover, by employing a gasphase reaction, the size of a reaction container can be reduced morewhen compared to the step of dehydration of an amide compound using aconventional liquid phase reaction. Therefore, according to the presentinvention, the step of regenerating the corresponding aromatic nitrilecompound from the aromatic amide compound can be easily industrialized.

Furthermore, according to the present invention, by producing thearomatic nitrile compound as described above, a method for efficientlyproducing a carbonate ester can also be realized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of an apparatus for producing a carbonate ester.

FIG. 2 schematically shows an apparatus for producing cyanopyridinewhich was used in working examples in which cyanopyridine was producedunder elevated pressure or ordinary pressure.

FIG. 3 schematically shows an apparatus for producing cyanopyridinewhich was used in working examples in which cyanopyridine was producedunder reduced pressure.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will bedescribed in detail.

<1. Method for Producing Aromatic Nitrile Compound>

In the method for producing an aromatic nitrile compound of the presentinvention, an aromatic amide compound such as pyridinecarboamide(2-pyridinecarboamide, 3-pyridinecarboamide or 4-pyridinecarboamide) isdehydrated in a gas phase and converted into an aromatic nitrilecompound such as cyanopyridine. Specifically, in the method forproducing an aromatic nitrile compound of the present invention, forexample, a dehydration reaction is caused by a contact step in which thearomatic amide compound is brought into contact with a catalyst carryinga basic metal oxide in a gas phase, thereby producing the aromaticnitrile compound.

(Reaction Substrate)

Examples of the aromatic amide compound to be used in the method forproducing an aromatic nitrile compound include amide compounds having anaromatic hydrocarbon ring such as a benzene ring, a naphthalene ring andan anthracene ring or a heteroaryl ring. Among these aromatic amidecompounds, an aromatic amide compound having a heteroaryl ring, i.e., aheteroaryl amide compound is preferably used, and examples of theheteroaryl amide compound include amide compounds having a pyridinering, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazinering, a pyrrole ring, a furan ring, a thiophene ring, an imidazole ring,a pyrazole ring, an oxazole ring or the like.

Preferred specific examples of the heteroaryl amide compound includethose having a pyridine ring such as pyridinecarboamide(2-pyridinecarboamide, 3-pyridinecarboamide and 4-pyridinecarboamide)described above.

The aromatic nitrile compound produced by the production method of thepresent invention is a product of a dehydration reaction correspondingto the above-described aromatic amide compound as is clear from theabove-described reaction formula. Accordingly, specific examples of thearomatic nitrile compound targeted in the production method of thepresent invention include a heteroaryl nitrile compound. Preferredspecific examples of the heteroaryl nitrile compound include thosehaving a pyridine ring such as cyanopyridine (2-cyanopyridine,3-cyanopyridine and 4-cyanopyridine).

(Catalyst)

In this regard, the catalyst to be used in the above-describeddehydration reaction of the present invention preferably includes anoxide of an alkali metal (K, Li, Na, Rb, Cs). In particular, as thecatalyst to be used in the above-described reaction, a catalystincluding an oxide of at least one of Na, K, Rb and Cs (cesium) ispreferably used. Further, as a carrier of the above-described catalyst,a substance generally serving as a catalyst carrier can be used, but asa result of examination of various carriers, it is preferred that SiO₂or ZrO₂ is included.

An example of the method for producing the catalyst to be used in thedehydration reaction of the present invention will be described below.In the case where the carrier is SiO₂, a commercially available powderedor spherical SiO₂ can be used, and it is preferred that the particlesize is adjusted to, for example, 4.0 mm or less so that an active metalcan be uniformly carried, and that pre-baking is carried out in the airat 700° C. for 1 hour for removing moisture. There are SiO₂ productswith various characteristics, but the larger the specific surface areais, the better it is because the active metal can be highly dispersedand the amount of the aromatic nitrile compound produced is improved.Specifically, the specific surface area is preferably 300 m²/g or more.However, the specific surface area of the catalyst after preparation maybe reduced to be less than the specific surface area of SiO₂ alone dueto the interaction between SiO₂ and the active metal or the like. Inthis case, the specific surface area of the catalyst after theproduction is preferably 150 m²/g or more. A metal oxide serving as anactive species can be carried according to an impregnation method suchas an incipient wetness method and an evaporation drying method.

It is sufficient when a metal salt that is a precursor of the catalystis water-soluble, and when it is an alkali metal, various compounds suchas a carbonate, a hydrogencarbonate, a chloride salt, a nitrate and asilicate can be used. A carrier is impregnated with an aqueous solutionof a precursor of a basic metal, followed by drying and baking, and thenthe obtained product can be used as the catalyst. The baking temperaturevaries depending on the precursor to be used, but it is preferably 400to 600° C.

Further, as the catalyst to be used in the present invention, a catalystin which only one or more alkali metal oxides are carried on a carrierconsisting of one or both of SiO₂ and ZrO₂ is preferred, but other thanthe above-described elements, the catalyst may contain an unavoidableimpurity mixed during the catalyst production process or the like.However, it is desirable that mixing of an impurity is suppressed asmuch as possible.

In this regard, the catalyst to be used in the present invention,wherein a metal oxide serving as an active species is carried on acarrier, may be in the form of either powder or a molded body, and inthe case of the molded body, it may be any of a spherical type, a pellettype, a cylinder type, a ring type, a wheel type, a granular type, etc.Further, the catalyst can be fixed to a support structure such as ahoneycomb and used.

The size of the carrier is not limited, but when using a sphericalcarrier, the average diameter of particles of the catalyst (carrierdiameter) is preferably 0.01 to 8.0 mm, more preferably 0.03 to 6.0 mm,and even more preferably 0.05 to 5.0 mm. By using the catalyst whosecarrier diameter is relatively larger than the average diameter (carrierdiameter) of particles of a catalyst to be used in a liquid phasereaction as described above, the flow channel of the reaction substratein the gas phase reaction is ensured, and a high space velocity can beprovided. Note that when using a fluidized bed in the gas phasereaction, a catalyst with a relatively small particle diameter ispreferably used so that the catalyst can be stirred with a small gasflow amount, and that when using a fixed bed in the gas phase reaction,a relatively large particle diameter or shape is preferred so that thegeneration of pressure loss can be prevented as much as possible.

The carrier diameter, i.e., the average diameter of particles of thecatalyst refers to the average diameter of particles of the wholecatalyst including a catalytic component and the carrier. The value ofthe carrier diameter of the catalyst is measured based on the sievingmethod: Test sieving—General requirements defined in JISZ8815 or thelike.

Further, the carrying amount of the catalyst may be suitably set, butbased on the total catalyst weight, the carrying amount in metalconversion of the active species such as an alkali metal oxide ispreferably 0.05 to 2.0 mmol/g, more preferably 0.10 to 1.5 mmol/g, andeven more preferably 0.30 to 1.0 mmol/g. Further, the amount of thecatalyst used during the reaction may also be suitably set.

(Reaction System and Reaction Container)

In the method for producing the aromatic nitrile compound of the presentinvention, it is preferred to use a gas phase reaction in which an amidecompound in the form of gas or mist is flowed through a catalyst layertogether with an inert gas, and a gas phase reaction apparatus with afixed bed or fluidized bed can be applied thereto. Thus, in the contactstep in which the aromatic amide compound is brought into contact withthe catalyst in the gas phase, the aromatic amide compound in acompletely vaporized state is preferably used, but the aromatic amidecompound in a state where mist is partially included in gas may also beused.

It is desirable that the method for producing the aromatic nitrilecompound is performed while removing produced by-product water by meansof a dehydration reaction. The present inventors diligently maderesearches and found that, for example, when a vaporizing chamber isattached to the upper portion of a reaction tube in which the catalystis put, the aromatic amide compound is dropped into the vaporizingchamber and the amide compound is passed through the catalyst layer inthe gas phase in a short time, the amount of the aromatic nitrilecompound produced can be improved, and the production of a by-productcan be suppressed.

(Inert Gas)

In the above-described dehydration reaction, it is preferred that aninert gas is brought into contact with the catalyst together with thearomatic amide compound in the gas phase. Specific examples of the inertgas to be used in the dehydration reaction include nitrogen gas and raregases such as helium and argon, and nitrogen gas is preferably used. Theflow rate, etc. of the inert gas will be described later.

(Solvent)

In the above-described dehydration reaction, a solvent can be used. Inparticular, in the step of vaporizing the aromatic amide compound whosemelting point is high, by mixing the aromatic amide compound with asolvent compatible therewith in advance and delivering the mixture, thetrouble of closure due to precipitation of the aromatic amide compoundcan be prevented. That is, it is preferred to use a solvent that iscompatible with the aromatic amide compound as the target of thedehydration reaction. The solvent compatible with the aromatic amidecompound includes not only a solvent which can be mixed with thearomatic amide compound at any ratio, but also a solvent which candissolve the aromatic amide compound as the target only to apredetermined degree of solubility, in an amount by which the aromaticamide compound can be dissolved to a concentration that is equal to orlower than the upper limit of the degree of solubility at apredetermined temperature. Further, it is preferred that the solvent isalso vaporized and used in the dehydration reaction (contact step). Theboiling point of the solvent that is vaporized and used in thedehydration reaction as described above is preferably 20° C. to 300° C.,more preferably 80° C. to 250° C., and even more preferably 110° C. to200° C. under ordinary pressure.

Specific examples of the solvent to be used in the dehydration reactioninclude a pyridine compound, a ketone compound, an ether compound, anester compound and an alcohol, and a pyridine compound, a ketonecompound, etc. are preferably used.

Examples of the pyridine compound, i.e., a compound having a pyridineskeleton serving as the solvent include 2-alkylpyridine, 3-alkylpyridineand 4-alkylpyridine such as 4-methylpyridine and pyridine. Inparticular, in the dehydration reaction in which pyridine may begenerated as a by-product, when using the pyridine compound as thesolvent with preferred conditions being set in advance, the step ofremoving pyridine as the main by-product is not required.

Further, examples of the ketone compound serving as the solvent includea cyclic ketone compound such as cyclopentanone and cyclohexane andacetone.

As the solvent for the dehydration reaction, it is preferred to use asolvent consisting of only one or more substances selected from theabove-described compounds, but a mixed solvent further containinganother compound may also be used.

(Conditions for Dehydration Reaction Including Contact Step)

As described above, the method for producing the aromatic nitrilecompound has a contact step for bringing the aromatic amide compoundinto contact with the catalyst in the gas phase during the dehydrationreaction.

In the contact step, the temperature at which the aromatic amidecompound, etc. are brought into contact with the catalyst is preferably170° C. or higher but lower than 300° C. The temperature is, forexample, 180° C. or higher but lower than 290° C., or 190° C. or higherbut lower than 280° C., more preferably 210° C. or higher but lower than280° C., and even more preferably 220° C. or higher but lower than 260°C. It is considered that the temperature at which the aromatic amidecompound, etc. are brought into contact with the catalyst is equal to,for example, the temperature of the inside of a reaction tube (reactioncontainer) to which the catalyst is fixed.

Further, the time for bringing the aromatic amide compound into contactwith the catalyst in the contact step, and in the case where an inertgas, a solvent, etc. are included together with the aromatic amidecompound, the time for bringing a mixed gas of these gaseouscompositions into contact with the catalyst are preferably 0.001 sec ormore or 0.005 sec or more, for example, 0.01 sec or more, but less than10 sec. The above-described time for contact with the catalyst is morepreferably 0.1 sec or more but less than 5 sec, and even more preferably0.5 sec or more but less than 2 sec.

Note that the time for contact with the catalyst is the average timeduring which the gas of the aromatic amide compound or theabove-described mixed gas is passed through the catalyst layer, and itis calculated from: Time for contact with catalyst (sec)=Height ofcatalyst layer in reactor (cm)÷Linear velocity of gas in reactor(cm/sec).

In the contact step, the molar ratio between the flow rate of thearomatic amide compound and the flow rate of the gaseous composition ispreferably 1:0 to 1:200, more preferably 1:1 to 1:100, and even morepreferably 1:1 to 1:20.

The space velocity (SV) of the whole gas component in the contact stepis preferably 1,000 to 50,000 (h⁻¹), more preferably 1,500 to 30,000(h⁻¹), and even more preferably 2,000 to 25,000 (h⁻¹). Further, whenperforming the contact step under reduced pressure, the space velocity(SV) of the whole gas component is preferably 1,000 to 1,000,000 (h⁻¹),more preferably 1,500 to 700,000 (h⁻¹), and even more preferably 1,900to 504,000 (h⁻¹).

Regarding conditions for the dehydration reaction, the pressure may bein the range of an elevated pressure (e.g., 506.5 (kPa)) to a reducedpressure (e.g., 0.1 (kPa)), but is not particularly limited thereto.

For example, the reaction pressure is 303.9 to 0.7 (kPa), preferably202.6 to 0.9 (kPa), and more preferably 101.3 to 1.0 (kPa).

Further, it is preferred that the aromatic amide compound is dehydratedwhen it is in the form of liquid before vaporized. When using amolecular sieve as a dehydrating agent, the type and form thereof arenot particularly limited, but for example, spherical or pellet-typemolecular sieves 3A, 4A, 5A, etc. generally having high waterabsorbability can be used. For example, ZEOLUM manufactured by TosohCorporation can be suitably used.

(Example of by-Product in Dehydration Reaction)

It is considered that in the dehydration reaction of the aromatic amidecompound, pyridine is by-produced via aromatic carboxylic acid due todecomposition of the aromatic amide compound as described above.However, almost no by-product such as pyridine shown in theabove-described formula is generated in the reaction solution after thedehydration reaction using the contact step of the present invention.

<2. Method for Producing Carbonate Ester Using Aromatic NitrileCompound>

By providing the contact step in the gas phase to the regeneration ofthe aromatic amide compound into the aromatic nitrile compound by meansof the dehydration reaction, the reaction rate was successfully improvedsignificantly to reduce the reaction time significantly. By this, itbecame possible to achieve a balance between the rate of regeneration ofthe aromatic amide compound into the aromatic nitrile compound by meansof the dehydration reaction and the rate of synthesis of a carbonateester from CO₂ and an alcohol using the aromatic nitrile compound, andit became possible to establish these reactions as a series ofcommercial processes. Accordingly, by applying this finding to a methodfor producing a carbonate ester, the present inventors successfullyconceived the below-described method for producing a carbonate ester.

(First Reaction Step)

The first reaction step in the method for producing a carbonate ester ofthe present invention includes a reaction in which an alcohol isdirectly reacted with carbon dioxide in the presence of a solid catalystcontaining, for example, CeO₂ (cerium oxide), etc. and the aromaticnitrile compound to produce the carbonate ester (carbonate esterproduction reaction).

In this step, when the alcohol is reacted with carbon dioxide, water isalso produced in addition to the carbonate ester, and by a hydrationreaction of the aromatic nitrile compound present in the reaction systemand produced water, an aromatic amide compound is produced, and theproduced water can be removed from the reaction system or reduced. Byefficiently removing water from the reaction system in this way, theproduction of the carbonate ester can be promoted. For example, it is asshown in formula below.

(Alcohol)

In this regard, as the alcohol, any alcohol selected from one or more ofa primary alcohol, a secondary alcohol and a tertiary alcohol can beused. For example, methanol, ethanol, 1-propanol, isopropanol,1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol,allyl alcohol, 2-methyl-1-propanol, cyclohexanemethanol, benzyl alcohol,ethylene glycol, 1,2-propanediol and 1,3-propanediol are preferably usedbecause a high yield of a product and a high reaction rate are obtained.In these cases, carbonate esters produced are respectively dimethylcarbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate,dibutyl carbonate, dipentyl carbonate, dihexyl carbonate, diheptylcarbonate, dioctyl carbonate, dinonane carbonate, diallyl carbonate,di-2-methyl-propyl carbonate, dicyclohexanemethyl carbonate, dibenzylcarbonate, ethylene carbonate, 1,2-propylene carbonate and 1,3-propylenecarbonate.

Further, in the first reaction step, an alcohol having 1 to 6 carbonatoms is preferably used, and an alcohol having 2 to 4 carbon atoms ismore preferably used. In particular, when using the carbonate esterobtained as a raw material of diaryl carbonate, the carbon number of thealcohol is preferably adjusted within the above-described range.

Further, in the first reaction step, a monohydric alcohol or a dihydricalcohol is preferably used.

(Catalyst for Production of Carbonate Ester)

Further, in the first reaction step in the production of the carbonateester, it is preferred to use one or both of CeO₂ and ZrO₂ as a solidcatalyst. For example, it is preferred to use only CeO₂, only ZrO₂, amixture of CeO₂ and ZrO₂, a solid solution or composite oxide of CeO₂and ZrO₂ or the like, and it is particularly preferred to use only CeO₂.The mixing ratio between CeO₂ and ZrO₂ in the solid solution orcomposite oxide thereof is basically 50:50, but can be suitably changed.

In this regard, the catalyst to be used in the first reaction step maybe in the form of either powder or a molded body, and in the case of themolded body, it may be any of a spherical type, a pellet type, acylinder type, a ring type, a wheel type, a granular type, etc.

(Carbon Dioxide)

As carbon dioxide to be used in the present invention, not only carbondioxide prepared as industrial gas, but also carbon dioxide separatedand recovered from exhaust gas of plants producing various products,ironworks, power plants, etc. can be used.

(Solvent for Carbonate Ester Production Reaction)

In the carbonate ester production reaction, it is preferred to use asolvent having a boiling point higher than that of the amide compound tobe produced. More preferably, the solvent in the carbonate esterproduction reaction contains at least one of dialkylbenzene,alkylnaphthalene and diphenylbenzene. Specific examples thereof includeBarrel Process Oil B28AN and Barrel Process Oil B30 (manufactured byMatsumura Oil Co., Ltd.), each of which contains components includingdialkylbenzene, alkylnaphthalene, diphenylbenzene, etc.

(Separation by Distillation)

After the reaction, a carbonate ester as the main product, an aromaticamide compound as a by-product, an unreacted aromatic nitrile compound,and a solid catalyst such as CeO₂ are separated by distillation, therebyrecovering the products.

(Second Reaction Step)

Next, in the second reaction step in the present invention, the aromaticamide compound by-produced in the first reaction step is preferablyseparated from the system obtained after the carbonate ester productionreaction, and then an aromatic nitrile compound is produced by means ofa dehydration reaction. The second reaction step corresponds to theabove-described method for producing the aromatic nitrite compound.Specifically, in the second reaction step for the production of thecarbonate ester, the aromatic nitrile compound is produced from thearomatic amide compound according to the technique described in thecolumn regarding the method for producing the aromatic nitrile compoundabove, thereby regenerating the aromatic nitrile compound. Accordingly,the details of the second reaction step are omitted.

(Reuse of Aromatic Nitrile Compound)

The aromatic nitrile compound regenerated in the second reaction stepcan be reused in the first reaction step (hydration reaction).

According to the present invention, as described above, by performingthe dehydration reaction of the aromatic amide compound in the gasphase, the aromatic nitrile compound can be efficiently regenerated fromthe aromatic amide compound while suppressing the generation of aby-product. Moreover, by fixing the catalyst in a reaction tube, thestep for subjecting the catalyst to solid-liquid separation is madeunnecessary and the aromatic nitrile compound can be easily recovered.Thus, in the present invention, it is possible to selectively regeneratethe aromatic nitrile compound from the aromatic amide compound, and topromote a series of reactions while separating the respective componentsonly by distillation without solid-liquid separation of the catalyst.Accordingly, an efficient process, which will be described in detaillater, can be realized.

<3. Apparatus for Producing Carbonate Ester>

Hereinafter, an apparatus for producing a carbonate ester to be used inthe present invention will be described in detail by way of a specificexample. FIG. 1 shows an example of a preferable apparatus.

(First Reaction Step)

In the first reaction step, raw materials, i.e., an alcohol (1-propanol(PrOH); liquid phase), 2-cyanopyridine (2-CP; liquid phase) and carbondioxide (CO₂; liquid phase, it may be supplied via a booster pump) arecontinuously supplied to a buffer tank 1 using a raw material feedpiping 31, a CO₂ recovery column top CO₂ transfer piping (CO₂ transferpiping at the top side of the CO₂ recovery column) 15, a carbonate esterrecovery column top liquid transfer piping (liquid transfer piping atthe top side of the carbonate ester recovery column) 19, and an amideseparation column top liquid transfer piping (liquid transfer piping atthe top side of the amide separation column) 21. This mixed solution ofthe raw materials is circulated between a fixed bed flow-type carbonateester reactor 2 in which a solid catalyst (solid phase) consisting ofone or both of CeO₂ and ZrO₂ is fixed to a support material (firstreaction portion) and the buffer tank 1 via a first reaction solutioncirculation piping 11 and a second reaction solution circulation piping12 using a pump (not shown), thereby synthesizing dipropyl carbonate(DPrC). The reaction solution containing DPrC is continuously withdrawnfrom the second reaction solution circulation piping 12 in the sameamount as the amount of the raw materials supplied to the buffer tank 1,recovered using a piping 13, and delivered to a DPrC recovery step. PrOHand CO₂ are recovered from the reaction solution and transferred to thebuffer tank 1 respectively via the carbonate ester recovery column topliquid transfer piping 19 and the CO₂ recovery column top CO₂ transferpiping 15, thereby reusing them. At the start of the reaction, new2-cyanopyridine is used, but 2-cyanopyridine regenerated from2-picolinamide is separated and purified in an amide separation column 6and transferred to the buffer tank 1 via the amide separation column topliquid transfer piping 21, thereby reusing it.

As a direct synthesis apparatus for a carbonate ester using CeO₂, ZrO₂,etc. as a solid catalyst (carbonate ester reactor 2), any of flowreactors such as a batch reactor, a semi-batch reactor, a continuoustank reactor and a tube reactor may be used. When a catalyst is fixed toa reactor, it is not necessary to filter and separate the catalyst. Forthis reason, a fixed bed reactor is preferred.

(Reaction Solution Temperature)

The reaction solution temperature in the carbonate ester reactor 2 ispreferably 50 to 300° C. When the reaction solution temperature is lowerthan 50° C., the reaction rate is low, the carbonate ester synthesisreaction and the hydration reaction with 2-cyanopyridine hardlyprogress, and the productivity of the carbonate ester tends to be low.When the reaction solution temperature is higher than 300° C., thereaction rate of each reaction is high, but the carbonate ester iseasily decomposed or denatured and 2-picolinamide is easily reacted withan alcohol. For this reason, the yield of the carbonate ester tends tobe low. The reaction solution temperature is more preferably 100 to 150°C. However, since it is considered that the ideal reaction solutiontemperature varies depending on the type and amount of the solidcatalyst and the amount and ratio of the raw materials (alcohol and2-cyanopyridine), it is desirable to suitably set optimum conditions.Since the preferred reaction solution temperature is 100 to 150° C., itis desirable to preheat the raw materials (alcohol and 2-cyanopyridine)with steam or the like on a stage before the carbonate ester reactor.

(Reaction Pressure)

The reaction pressure in the carbonate ester reactor 2 is preferably 0.1to 20 MPa (absolute pressure). When the reaction pressure is lower than0.1 MPa (absolute pressure), a decompression device is required. As aresult, facilities are complicated and the cost is increased, and inaddition, a power energy for reducing the pressure is required,resulting in decrease of the energy efficiency. When the reactionpressure is higher than 20 MPa, the hydration reaction with2-cyanopyridine does not easily progress, resulting in decrease of theyield of the carbonate ester. In addition, a power energy for increasingthe pressure is required, resulting in decrease of the energyefficiency. From the viewpoint of increasing the yield of the carbonateester, the reaction pressure is more preferably 0.5 to 15 MPa (absolutepressure), and even more preferably 1.0 to 10 MPa (absolute pressure).

(Amount of 2-Cyanopyridine)

2-cyanopyridine to be used for the hydration reaction is preferably usedin a molar quantity that is 0.1 to 5 times the theoretical molarquantity of water by-produced by the reaction of the alcohol and CO₂ asthe raw materials, and it is desirably introduced into the reactorbefore the reaction. The molar quantity of 2-cyanopyridine is moredesirably 0.2 to 3 times, and particularly desirably 0.3 to 1.5 timesthe theoretical molar quantity of water by-produced by the reaction ofthe alcohol and CO₂ as the raw materials. When the molar quantity of2-cyanopyridine is too small, since the amount of 2-cyanopyridinecontributing to the hydration reaction is small, the yield of thecarbonate ester may be decreased. Meanwhile, when 2-cyanopyridine isintroduced in an excess molar quantity relative to the alcohol as theraw material, the side reaction of 2-cyanopyridine is increased, andtherefore it is undesirable. Since it is considered that the idealamounts of the alcohol and 2-cyanopyridine relative to the solidcatalyst vary depending on the type and amount of the solid catalyst,the type of the alcohol and the ratio between the alcohol and2-cyanopyridine, it is desirable to suitably set optimum conditions.

(Separation of Reaction Products)

Preferably, the separation of reaction products is entirely performed bymeans of distillation. After the reaction in the carbonate ester reactor2, a reaction solution 13 is transferred to a CO₂ recovery column 3. Amixture of PrOH, DPrC, 2-cyanopyridine and 2-picolinamide is recoveredfrom the bottom of the CO₂ recovery column 3 via a CO₂ recovery columnbottom liquid transfer piping 14, and CO₂ is recovered from the top ofthe CO₂ recovery column 3 via the CO₂ recovery column top CO₂ transferpiping 15. The recovered CO₂ is transferred to the buffer tank 1 andrecycled in the reaction in the carbonate ester reactor 2.

The mixture recovered from the CO₂ recovery column 3 is transferred to adehydrating agent separation column 4 via the CO₂ recovery column bottomliquid transfer piping 14. A mixture of 2-cyanopyridine and2-picolinamide is recovered from the bottom of the dehydrating agentseparation column 4 via a dehydrating agent separation column bottomliquid transfer piping 16, and PrOH and DPrC are recovered from the topof the dehydrating agent separation column 4 via a dehydrating agentseparation column top liquid transfer piping 17.

The mixture recovered from the bottom of the dehydrating agentseparation column 4 is transferred to the amide separation column 6 viathe dehydrating agent separation column bottom liquid transfer piping16. 2-picolinamide (20) is recovered from the bottom of the amideseparation column 6, and 2-cyanopyridine is recovered from the top ofthe amide separation column 6. The recovered 2-cyanopyridine istransferred to the buffer tank 1 via the amide separation column topliquid transfer piping 21 and recycled in the reaction in the carbonateester reactor 2.

PrOH and DPrC recovered from the top of the dehydrating agent separationcolumn 4 is transferred to a carbonate ester recovery column 5 via thedehydrating agent separation column top liquid transfer piping 17. DPrCis recovered from the bottom of the carbonate ester recovery column 5via a carbonate ester recovery column bottom liquid transfer piping 18,and PrOH is recovered from the top of the carbonate ester recoverycolumn 5 via the carbonate ester recovery column top liquid transferpiping 19. The recovered PrOH is transferred to the buffer tank 1 andrecycled in the reaction in the carbonate ester reactor 2.

(Second Reaction Step)

In the second reaction step, 2-cyanopyridine is produced by adehydration reaction of 2-picolinamide in a nitrile regeneration gasphase reactor 8.

2-picolinamide recovered from the amide separation column 6 istransferred to a vaporizer 7 via an amide separation column bottomliquid transfer piping 20. Preferably, it is mixed with an inert gasthat is nitrogen or the like, the mixture is heated to a temperaturenear the boiling point of amide to provide a gas or a mixed gasconsisting of gas and droplets, and it is transferred to the nitrileregeneration gas phase reactor 8 via a vaporizer-nitrile regenerationgas phase reactor connection piping 22. The form of the vaporizer 7 forvaporizing the amide compound, etc. is not particularly limited, and anyof an ejector type vaporizer, a contact type vaporizer, a bubblingdevice, etc. may be used.

In the apparatus for producing a nitrile compound to be used in thepresent invention (nitrile regeneration gas phase reactor 8),2-picolinamide, and preferably, an inert gas that is nitrogen or thelike, etc. are brought into contact with a catalyst containing a carriedbasic metal oxide in the gas phase to cause a dehydration reaction of2-picolinamide. By this dehydration reaction, 2-cyanopyridine isproduced. When transferring the amide compound, for the purpose ofpreventing the trouble of closure, the amide compound can be dissolvedin a transfer solvent to transfer the liquid. When using an amidetransfer solvent, it is preferred that the solvent is also vaporizedtogether with amide to perform a nitrile regeneration gas phasereaction. In this case, a solvent vapor can be used instead of the inertgas.

The form of the nitrile regeneration gas phase reactor 8 is notparticularly limited. It is preferred to use a gas phase reaction inwhich the amide compound in the form of gas or mist is flowed throughthe catalyst layer together with the inert gas and the like, and a gasphase reaction apparatus with a fixed bed, fluidized bed or the like canbe applied thereto.

Thus, for efficiently promoting the dehydration reaction by bringing2-picolinamide into contact with the catalyst, etc. in the gas phase,the above-described various reaction conditions related to thedehydration reaction or reaction conditions described in the Examplesbelow are appropriately employed.

The mixed gas containing 2-cyanopyridine is transferred from the gasphase reactor 8 to an H₂O separation apparatus 9 via a gas phasereaction product transfer piping 23. Water and nitrogen gas areseparated from the mixed gas in the H₂O separation apparatus 9, and2-cyanopyridine and 2-picolinamide recovered are transferred from theH₂O separation apparatus 9 to the amide separation column 6 via a highboiling transfer piping 24. Further, 2-picolinamide is recovered fromthe bottom of the amide separation column 6 via the amide separationcolumn bottom liquid transfer piping 20 and transferred to the vaporizer7, and 2-cyanopyridine is recovered from the top of the amide separationcolumn 6. 2-cyanopyridine recovered is transferred to the buffer tank 1via the amide separation column top liquid transfer piping 21 andrecycled in the reaction in the carbonate ester reactor 2.

Further, nitrogen gas and water separated in the H₂O separationapparatus 9 are transferred to an N₂ recovery apparatus 10 via a lightboiling transfer piping 25, and water is separated in the N₂ recoveryapparatus 10 to recover nitrogen gas. Water separated in the N₂ recoveryapparatus 10 is transferred to the outside of the carbonate esterapparatus via an N₂ recovery apparatus water transfer piping 26.Nitrogen gas recovered in the N₂ recovery apparatus 10 is transferred tothe vaporizer 7 via an N₂ recovery apparatus N₂ transfer piping 27, andit can be used in the gas phase reaction. In the case of using an amidecompound transfer solvent, a step of recovering the solvent is providedseparately, thereby reusing the solvent for transferring the amidecompound. The form of each of the H₂O separation apparatus 9 and the N₂recovery apparatus 10 is not particularly limited, and any of a coolingsystem, a membrane separation apparatus, etc. may be used.

As described above, in the present invention, dehydration of the amidecompound can be promoted by the contact step in the gas phase, and inaddition, the reaction product and compounds to be reused can beseparated by distillation or the like without solid-liquid separation.For this reason, according to the present invention, it is possible toefficiently produce a carbonate ester in a smaller number of productionsteps while simplifying apparatuses.

EXAMPLES

Hereinafter, the present invention will be more specifically describedby way of examples, but the present invention is not limited thereto.Firstly, examples and comparative examples of the method for producingcyanopyridine will be described below.

Example 1

SiO₂ as a carrier (manufactured by Fuji Silysia Chemical Ltd., CARiACT,Q-6 (carrier diameter: 0.075 to 0.15 mm)) was pre-baked at 700° C. forabout 1 hour. After that, for carrying Cs as an alkali metal, an aqueoussolution was prepared using Cs₂CO₃ (manufactured by Wako Pure ChemicalIndustries, Ltd.) such that the final amount of Cs metal to be carriedwould be 0.5 mmol/g, and SiO₂ was impregnated with the aqueous solution.After that, the obtained material was dried at 110° C. for about 6 hoursand then baked at 500° C. for about 3 hours, thereby obtaining aCs₂O/SiO₂ catalyst.

A reaction tube 40 made of SUS 304 having an inner diameter of 10.7 mmand a length of 30 cm was filled with the catalyst produced by theabove-described production method (see FIG. 2 ). Further, immediatelyabove the reaction tube 40, a vaporizing chamber 42 made of SUS 304having an inner diameter of 10.7 mm and a length of 30 cm filled withRaschig ring was provided.

10 g of 2-picolinamide (2-PA) was dissolved in 4-methylpyridine servingas a transfer solvent (90 g), and the mixture was put into a rawmaterial container 44. The raw material container 44 was placed on aprecision balance, a suction tube with a filter was dropped into the rawmaterial solution, and the balance was stabilized.

Nitrogen was flowed through the vaporizing chamber 42 connected to theraw material container 44, and the reaction tube 40 at a flow rate of1000 mL/min, and the vaporizing chamber 42 and the reaction tube 40 wereheated to 230° C. respectively with mantle heaters 46 and 48. Further, apiping 50 for feeding nitrogen and a piping at the exit side of thereaction tube 40 were kept at 150° C. For recovering a reaction product,a water cooling trap container 52 was located at the first stage, a dryice/methanol cooling trap container 54 was located at the second stage,and a liquid nitrogen cooling trap container (not shown) was located atthe final stage.

After the temperature of the catalyst layer became stable, a plungerpump 56 was started, and a reaction was performed for the time describedin the column of the catalyst contact time in the table below. Duringthe reaction, excessive pressurization was prevented by a pressurelimiter 58 so that the pressure in the reaction system of thecyanopyridine production apparatus shown in FIG. 2 did not exceed 506.5(kPa).

The conditions for the above-described contact reaction (dehydrationreaction) were as shown in Table 1. After the reaction was completed,the obtained reaction product was recovered and analyzed with GC-FID.

The analysis conditions for the results of the contact reaction(dehydration reaction) were as shown below.

[Analysis Conditions]

(GC-FID)

Shimadzu GC-2014, column: TC-17 (length: 30 m, inner diameter: 0.25mmID, thickness of liquid phase: 0.25 μm)

Temperature of vaporizing chamber: 250° C., Detector: 260° C., CarrierHe: 175 kPa, Flow rate of column: 2.5 mL/min, Split ratio: 50

Temperature program: [kept at 70° C. for 5 min]→[elevated to 190° C.,12° C./min]→[kept at 190° C. for 5 min]→[elevated to 250° C., 12°C./min]→[kept at 250° C. for 10 min][24-hour yield per 1 g of catalyst (mmol/24 hr·g)]=(Recovery amount ofproduct after 24-hour reaction (mmol))/(Amount of catalyst (g))[Space velocity: SV (hr⁻¹)]=(Amount of gas passed through catalyst layer(L·hr⁻¹))/(Amount of catalyst (L))Amount of gas: the sum of volumes of gases of nitrogen, 2-PA and solvent(L·hr⁻¹)[Catalyst filling height (height of catalyst layer in reactor)]: heightof catalyst filled in reaction tube (cm)[Catalyst contact time (sec)]=[Catalyst filling height (cm)]/[Linearvelocity (linear velocity of gas in reactor) (cm/sec)][Carrier Diameter of Catalyst]

The value of the carrier diameter of the catalyst is measured based onthe sieving method: Test sieving—General requirements defined in JIS Z8815.

Examples 2-15

In Example 2 or later, a reaction was performed in a manner similar tothat in Example 1, except that the conditions were changed as shown inTable 1. The results are shown in Table 1.

In each of the Examples and Comparative Examples, the active componentof the catalyst was Cs₂O; CARiACT Q-6 (the main component is SiO₂)manufactured by Fuji Silysia Chemical Ltd. was used as the carrier; andthe amount of an active metal carried by the catalyst (carrying amountin metal conversion of the active species based on the total catalystweight) was 0.5 mmol/g. Further, in each of the Examples and ComparativeExamples, 2-picolinamide (2-PA) was used as the aromatic amide compound.

Example 16

Unlike Examples 1-15, in Example 16, the contact reaction (dehydrationreaction) of the aromatic amide compound was performed under reducedpressure. Specifically, it was performed as described below.

100 g of 2-picolinamide (2-PA) was dissolved in cyclopentanone servingas a transfer solvent (900 g), and the mixture was put into a rawmaterial container.

Nitrogen was flowed through a reaction line (from an ejector 62 to atrap 64 shown in FIG. 3 ) connected to the raw material container 60 ata flow rate of 1000 mL/min. After the feed of nitrogen was stopped, avacuum pump 66 was connected to the trap 64, and the pressure in thereaction system was reduced to 0.5 kPa. A vaporizer 68 and a reactor 70were heated to 220° C. respectively with electric furnaces (not shown).Further, a piping at the exit side of the reaction line was heated to150° C. using a ribbon heater (not shown). For recovering a reactionproduct, a dry ice/methanol cooling trap container 64 was located (afirst fraction trap 64A and a recovery trap 64B in FIG. 3 ), and next tothat, a liquid nitrogen cooling trap container (not shown) was located.

After the temperature of the catalyst layer (not shown) placed in thereactor 70 became stable, a plunger pump 72 was started, and a reactionwas performed. For 90 minutes from the time when the inside of thecatalyst layer reached the steady state, a reaction product wasrecovered with the recovery trap 64B. During the reaction, the pressurein the reaction system of the cyanopyridine production apparatus shownin FIG. 3 was controlled with a pressure reduction controller 74 and aneedle valve 76. Note that until the inside of the catalyst layerreached the steady state, and after the reaction product was recoveredwith the recovery trap 64B after the inside of the catalyst layerreached the steady state, the reaction product was recovered with thefirst fraction trap 64A.

The conditions for the above-described contact reaction (dehydrationreaction) were as shown in Table 1. After the reaction was completed,the obtained reaction product was recovered and analyzed with GC-FID.

Examples 17-21

In Example 17 or later, a reaction was performed in a manner similar tothat in Example 16, except that the conditions were changed as shown inTable 1.

The results of Examples 1-21 are shown in Table 1 below.

TABLE 1 24-hour yeild per 1 g Catalyst Flow Molar flow rate SpaceCatalyst Temperature Temperature of catalyst filling rate Transfervelocity Linear contact of vaporizing of reactoin Reaction 2-CP PyridineCarrier Amount of height Transfer of N₂ 2-Pa solvent N₂ SV velocity timechamber tube pressure 2-CP Pyridine mmol/ mmol/ Examples diameter mmcatalyst g cm solvent mL/min mmol/h mmol/h mmol/h h − 1 cm/sec sec ° C.° C. kPa mmol/h mmol/h g · 24 h g · 24 h 1 0.075 to 0.15 1.7990 3.89 4-1000 33.8 398 2679 19905 21.5 0.18 230 225 303.9 9.6 0.0 128 0.00methyl- pyridine 2 0.075 to 0.15 1.7990 3.89 4- 1000 33.8 399 2679 1991121.5 0.18 250 247 303.9 18.7 0.0 250 0.00 methyl- pyridine 3 0.075 to0.15 1.7990 3.89 4- 1000 78.9 414 2679 20300 21.9 0.18 230 225 303.916.7 0.0 223 0.00 methyl- pyridine 4 0.075 to 0.15 1.7990 3.89 4- 100032.6 171 2893 19820 21.4 0.18 230 225 303.9 10.9 0.0 145 0.00 methyl-pyridine 5  1.7 to 4.0 9.0020 15.57 4- 1000 38.0 447 2679 5062 21.9 0.71230 225 101.3 10.7 0.0 28.6 0.00 methyl- pyridine 6  1.7 to 4.0 9.002015.57 — 1000 19.5 0 2679 4317 18.7 0.83 250 247 101.3 11.5 0.0 30.8 0.007  1.7 to 4.0 9.0020 15.57 — 1000 90.1 0 2679 4430 19.2 0.81 250 248101.3 23.1 0.0 61.5 0.00 8  1.7 to 4.0 2.1500 3.89 Cyclo- 250 697 954670 14851 16.1 0.24 250 243 101.3 22.2 0.0 248.3 0.00 pentanone 9  1.7to 4.0 2.1500 3.89 Cyclo- 0 378 337 0 4576 4.9 0.79 250 245 101.3 9.50.0 106.3 0.00 pentanone 10  1.7 to 4.0 2.1500 3.89 Cyclo- 0 93 68 01028 1.1 3.50 250 245 101.3 2.9 3.6 31.8 39.96 pentanone 11  1.7 to 4.02.1500 3.89 Cyclo- 0 61 629 0 4417 4.8 0.82 265 259 101.3 1.7 0.0 18.70.00 pentanone 12  1.7 to 4.0 2.1500 3.89 Cyclo- 250 45 60 603 4530 4.90.79 255 249 101.3 0.6 0.0 6.3 0.00 pentanone 13  1.7 to 4.0 9.002015.57 Cyclo- 1000 26 34 2679 4382 19.0 0.82 250 247 101.3 13.4 0.0 35.70.00 pentanone 14  1.7 to 4.0 9.0020 15.57 Cyclo- 1000 65 85 2679 452719.6 0.80 250 246 101.3 23.6 0.0 63.0 0.00 pentanone 15  1.7 to 4.09.0020 15.57 Cyclo- 1000 178 238 2679 4951 21.4 0.73 250 246 101.3 38.70.0 103.1 0.00 pentanone 16  1.7 to 4.0 250.17 32.5 Cyclo- 0 97 1191 08133 73 0.44 188 224 1.4 58.5 0.7 5.6 0.066 pentanone 17  1.7 to 4.0250.17 32.5 Cyclo- 0 88 1117 0 9835 89 0.37 168 186 1.0 18.9 0.1 1.80.007 pentanone 18  1.7 to 4.0 250.17 32.5 Cyclo- 0 119 470 0 1923 171.87 165 185 2.1 21.8 1.1 2.1 0.109 pentanone 19  1.7 to 4.0 250.17 32.5Cyclo- 0 81 127 0 2404 22 1.50 166 187 0.7 10.9 0.4 1.0 0.039 pentanone20 0.075 to 0.15 5.04 0.7 Cyclo- 0 88 1118 0 503741 95 0.01 186 220 1.06.4 0 30.7 0.00 pentanone 21 0.075 to 0.15 15.3 2.1 Cyclo- 0 89 1137 0189040 109 0.02 185 225 0.9 10.7 0 16.7 0.00 pentanone

Comparative Examples 1-9

In Comparative Examples 1-9, a solvent was used for removing waterproduced by the reaction to the outside of the reaction system, and adehydration reaction was performed in a liquid phase.

Comparative Example 1

SiO₂ as a carrier (manufactured by Fuji Silysia Chemical Ltd., CARiACT,Q-6 (carrier diameter: 0.075 to 0.15 mm)) was pre-baked at 700° C. forabout 1 hour. After that, for carrying Cs as an alkali metal, an aqueoussolution was prepared using Cs₂CO₃ (manufactured by Wako Pure ChemicalIndustries, Ltd.) such that the final amount of Cs metal to be carriedwould be 0.5 mmol/g, and SiO₂ was impregnated with the aqueous solution.After that, the obtained material was dried at 110° C. for about 6 hoursand then baked at 500° C. for about 3 hours, thereby obtaining aCs₂O/SiO₂ catalyst.

Next, a three-necked round-bottom flask was used as a reactor, and amagnetic stirring bar, the above-described Cs₂O/SiO₂ catalyst,2-picolinamide (manufactured by Tokyo Chemical Industry Co., Ltd.) and1,3-dimethoxybenzene (manufactured by Tokyo Chemical Industry Co., Ltd.)were introduced into the reactor.

Further, a thermometer and an air cooling tube containing 10 g ofmolecular sieve 4A were attached to the reactor, and a Liebig condenseris attached to the upper end of the air cooling tube to provide areaction apparatus.

Subsequently, the reaction solution was heated under ordinary pressureand kept in a boiled state, and by-product water was adsorbed to themolecular sieve without being returned to the reactor to performdehydration, thereby performing the reaction.

The reaction was started when the reaction solution started to boil, andthe reaction was performed for 24 hours.

After the reaction, the temperature was decreased to room temperature.The reaction solution was sampled and diluted two-fold with ethanol, and1-hexanol was added thereto as an internal standard substance. Theresultant substance was subjected to qualitative analysis with GC-MS(gas chromatograph-mass spectrometer) and to quantitative analysis withGC-FID.

Comparative Examples 2-7

In Comparative Examples 2-7, a reaction was performed in a mannersimilar to that in Comparative Example 1, except that the conditionswere changed as shown in Table 2.

Comparative Examples 8-9

In Comparative Examples 8-9, the conditions were changed as shown inTable 2, and in addition, the apparatus configuration and reactionconditions were changed as described below, thereby performing areaction.

SiO₂ as a carrier (manufactured by Fuji Silysia Chemical Ltd., CARiACT,Q-6 (carrier diameter: 0.075 to 0.15 mm)) was sized to 100 mesh or lessand pre-baked at 700° C. for about 1 hour. After that, for carrying Csas an alkali metal, an aqueous solution was prepared using Cs₂CO₃(manufactured by Wako Pure Chemical Industries, Ltd.) such that thefinal amount of Cs metal to be carried would be 0.5 mmol/g, and SiO₂ wasimpregnated with the aqueous solution. After that, the obtained materialwas dried at 110° C. for about 6 hours and then baked at 500° C. forabout 3 hours, thereby obtaining a Cs₂O/SiO₂ catalyst.

Next, a three-necked round-bottom flask was used as a reactor, and amagnetic stirring bar, the above-described Cs₂O/SiO₂ catalyst,2-picolinamide (manufactured by Tokyo Chemical Industry Co., Ltd.) anddiphenyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) wereintroduced into the reactor.

Further, a thermometer and a first air cooling tube as a distillationcolumn were attached to the reactor, a distilling head equipped with athermometer was attached to the upper end of the first air cooling tube,and a second air cooling tube, a receiver and a vacuum pump wereconnected to the distilling head to provide a reaction distillationapparatus. Note that a ribbon heater was wound around the first aircooling tube for adjusting the temperature. Further, a cooling trap wascooled with liquid nitrogen for recovering vaporized pyridine.

Subsequently, the pressure in the reaction distillation apparatus wasreduced to 13.3 kPa (100 Torr) using the vacuum pump. The first aircooling tube was heated to 60° C., which was higher than the boilingpoint of water and lower than the boiling point of diphenyl ether underthe reaction pressure. The reaction solution was maintained in a boiledstate at 184° C., which was equal to or higher than the boiling point ofdiphenyl ether and lower than the boiling point of 2-picolinamide underthe reaction pressure. By adjusting the temperature in this manner,partially vaporized diphenyl ether in the reaction system was cooled inthe first air cooling tube and returned to the reactor while theby-product water was distilled away to the outside of the system withoutbeing returned to the reactor, thereby performing the reaction.

The reaction was started when the reaction solution started to boil, andthe reaction was performed for 24 hours.

After the reaction, the temperature was decreased to room temperature.The reaction solution was sampled and diluted two-fold with ethanol, and1-hexanol was added thereto as an internal standard substance. Theresultant substance was subjected to qualitative analysis with GC-MS(gas chromatograph-mass spectrometer) and to quantitative analysis withGC-FID.

The results of Comparative Examples 1-9 are shown in Table 2 below.

TABLE 2 24-hour yield per Amount Amount Amount Temperature 1 g ofcatalyst Carrier of of of of reaction Reaction 2-CP Pyridine Comparativediameter catalyst solvent substrate solution pressure 2-CP Pyridinemmol/ mmol/ Examples mm g Liquid phase solvent mL mmol ° C. kPa mmolmmol g · 24 h g · 24 h 1 0.075 to 0.15 0.31 1,3-dimethoxybenzene 60 15.0215 101.3 10.4 0.13 33.5 0.42 (boiled) 2 0.075 to 0.15 0.31 1,2,3,4- 6015.0 210 101.3 8.47 0.10 27.3 0.31 tetrahydronaphthalene (boiled) 30.075 to 0.15 0.31 1,2-dimethoxybenzene 60 15.0 210 101.3 8.18 0.07 26.40.22 (boiled) 4 0.075 to 0.15 0.31 1,3,5-trimethoxybenzene 60 15.0 203101.3 2.27 0.15 7.32 0.49 (not boiled) 5 0.075 to 0.15 0.311,3,5-trimethylbenzene 60 15.0 165 101.3 2.70 0.00 8.7 0.00 (boiled) 6 1.7 to 4.0 0.31 1,3,5-trimethylbenzene 60 15.0 165 101.3 0.29 0.00 0.90.00 (boiled) 7  1.7 to 4.0 3.0 1,3,5-trimethylbenzene 60 15.0 165 101.35.00 0.015 1.67 0.005 (boiled) 8 0.075 to 0.15 1.0 Diphenyl ether 20048.0 181 13.3 23.4 0.14 23.4 0.14 (boiled) 9  1.7 to 4.0 1.0 Diphenylether 200 48.0 181 13.3 2.47 0.015 2.47 0.015 (boiled)

With reference to the attached drawings, the preferred embodiments ofthe present invention are described in detail above, but the presentinvention is not limited to the examples. Those skilled in the art ofthe present invention would obviously conceive any of various altered ormodified examples within the scope of the technical idea recited in theclaims, and it is understood that such altered or modified examples areduly encompassed in the technical scope of the present invention.

DESCRIPTION OF REFERENCE NUMERALS

-   1 buffer tank (CO₂, PrOH, DPrC, 2-CP, 2-PA)-   2 carbonate ester reactor (CO₂, PrOH, DPrC, 2-CP, 2-PA, fixed    catalyst)-   3 CO₂ recovery column (CO₂, PrOH, DPrC, 2-CP, 2-PA)-   4 dehydrating agent separation column (PrOH, DPrC, 2-CP, 2-PA)-   5 carbonate ester recovery column (PrOH, DPrC)-   6 amide separation column (2-CP, 2-PA)-   7 vaporizer (N₂, 2-PA)-   8 nitrile regeneration gas phase reactor (N₂, H₂O, 2-CP, 2-PA,    catalyst)-   9 H₂O separation apparatus (N₂, H₂O, 2-CP, 2-PA)-   10 N₂ recovery apparatus (N₂, H₂O)-   11 first reaction solution circulation piping (CO₂, PrOH, DPrC,    2-CP, 2-PA)-   12 second reaction solution circulation piping (CO₂, PrOH, DPrC,    2-CP, 2-PA)-   13 reaction solution withdrawing piping (CO₂, PrOH, DPrC, 2-CP,    2-PA)-   14 CO₂ recovery column bottom liquid transfer piping (PrOH, DPrC,    2-CP, 2-PA)-   15 CO₂ recovery column top CO₂ transfer piping (CO₂)-   16 dehydrating agent separation column bottom liquid transfer piping    (2-CP, 2-PA)-   17 dehydrating agent separation column top liquid transfer piping    (PrOH, DPrC)-   18 carbonate ester recovery column bottom liquid transfer piping    (DPrC)-   19 carbonate ester recovery column top liquid transfer piping (PrOH)-   20 amide separation column bottom liquid transfer piping (2-PA)-   21 amide separation column top liquid transfer piping (2-CP)-   22 vaporizer-nitrile regeneration gas phase reactor connection    piping (N₂, 2-PA)-   23 gas phase reaction product transfer piping (N₂, H₂O, 2-CP, 2-PA)-   24 H₂O separation apparatus high boiling transfer piping (2-CP,    2-PA)-   25 H₂O separation apparatus light boiling transfer piping (N₂, H₂O)-   26 N₂ recovery apparatus water transfer piping (H₂O)-   27 N₂ recovery apparatus N₂ transfer piping (N₂)-   31 raw material feed piping (CO₂, PrOH)-   40 reaction tube-   42 vaporizing chamber-   44 raw material container-   46, 48 mantle heater-   50 nitrogen gas feed piping-   52 water cooling trap container-   54 dry ice/methanol cooling trap container-   56 plunger pump-   58 pressure limiter-   60 raw material container-   62 ejector-   64 trap-   64A first fraction trap-   64B recovery trap-   66 vacuum pump-   68 vaporizer-   70 reactor-   72 plunger pump-   74 pressure reduction controller-   76 needle valve

The invention claimed is:
 1. A method for producing an aromatic nitrilecompound, the method comprising a dehydration reaction, wherein anaromatic amide compound is dehydrated, the method having a contact stepfor bringing the aromatic amide compound into contact with a catalyst ina gas phase during the dehydration reaction, wherein the aromatic amidecompound in the form of gas or mist is flowed through a catalyst layerin the contact step.
 2. The method for producing an aromatic nitrilecompound according to claim 1, wherein the catalyst is a catalystcarrying a metal oxide, where the metal of the metal oxide is an alkalimetal selected from the group consisting of K, Li, Na, Rb, and Cs. 3.The method for producing an aromatic nitrile compound according to claim1, wherein the aromatic amide compound is an aromatic amide compoundhaving an aromatic hydrocarbon ring, where the aromatic hydrocarbon ringis selected from the group consisting of a benzene ring, a naphthalenering, an anthracene ring and a heteroaryl ring.
 4. The method forproducing an aromatic nitrile compound according to claim 3, wherein thearomatic amide compound having an aromatic hydrocarbon ring is thearomatic amide compound that has the heteroaryl ring as the aromatichydrocarbon ring, and the heteroaryl ring is selected from the groupconsisting of 2-picolinamide, 3-pyridinecarboamide and4-pyridinecarboamide.
 5. The method for producing an aromatic nitrilecompound according to claim 1, wherein in the contact step, an inert gasand/or a solvent in a vaporized state is further brought into contactwith the catalyst.
 6. The method for producing an aromatic nitrilecompound according to claim 5, wherein the inert gas is selected fromthe group consisting of nitrogen gas, helium gas and argon gas.
 7. Themethod for producing an aromatic nitrile compound according to claim 5,wherein the boiling point of the solvent is 20° C. to 300° C.
 8. Themethod for producing an aromatic nitrile compound according to claim 5,wherein the solvent is compatible with the aromatic amide, wherein thesolvent compatible with the aromatic amide compound comprises solventswhich can be mixed with the aromatic amide compound at any ratio, andsolvents which can dissolve the aromatic amide compound as the targetonly to a predetermined degree of solubility, in an amount by which thearomatic amide compound can be dissolved to a concentration that isequal to or lower than the upper limit of the degree of solubility. 9.The method for producing an aromatic nitrile compound according to claim5, wherein the solvent is selected from the group consisting of apyridine compound and/or a ketone compound, an ether compound, an estercompound and an alcohol.
 10. The method for producing an aromaticnitrile compound according to claim 1, wherein in the contact step, thetemperature at which the aromatic amide compound is brought into contactwith the catalyst in the gas phase is 170° C. or higher but lower than300° C.
 11. The method for producing an aromatic nitrile compoundaccording to claim 1, wherein the time for bringing the aromatic amidecompound into contact with the catalyst in the gas phase is 0.001 sec ormore but less than 10 sec.